# US 11,309,862 B2 · Acoustic wave device, high frequency front end circuit, and communication apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,309,862 B2 - Document ID: US11309862B2 - Status: Granted - Kind: B2 - Application number: 16/718,295 - Filed: 2019-12-18 - Published: 2020-04-23 - Granted: 2022-04-19 - Earliest claimed: 2017-06-23 - Assignees: Murata Manufacturing Co., Ltd. - Applicants: Murata Manufacturing Co., Ltd. - Inventors: Yutaka Kishimoto - Web page: https://patentgrep.com/patent/US11309862B2 ## CPC - H03H 9/02952: {of parasitic capacitance} - H03F 1/56: Modifications of input or output impedances, not otherwise provided for - H03F 3/189: High-frequency amplifiers, e.g. radio frequency amplifiers - H03F 3/24: of transmitter output stages - H03H 3/02: for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) - H03H 3/10: for obtaining desired frequency or temperature coefficient - H03H 9/02228: {Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer} - H03H 9/02834: {of temperature influence (cut angles H03H9/02543)} - H03H 9/02866: {of bulk wave excitation and reflections} - H03H 9/02992: {Details of bus bars, contact pads or other electrical connections for finger electrodes} - H03H 9/0561: {consisting of a multilayered structure} - H03H 9/145: for networks using surface acoustic waves - H03H 9/175: {Acoustic mirrors} - H03H 9/25: Constructional features of resonators using surface acoustic waves {(devices for manipulating acoustic surface waves in general G10K11/36)} - H03H 9/6483: {Ladder SAW filters} - H03F 3/20: Power amplifiers, e.g. Class B amplifiers, Class C amplifiers (H03F3/26 - H03F3/30 take precedence) - H03F 2200/165: A filter circuit coupled to the input of an amplifier - H03F 2200/171: A filter circuit coupled to the output of an amplifier - H03F 2200/294: the amplifier being a low noise amplifier [LNA] - H03F 2200/451: the amplifier being a radio frequency amplifier - H03H 2003/025: {the resonators or networks comprising an acoustic mirror} - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - H03F: AMPLIFIERS ## Abstract An acoustic wave device includes in order a substrate, an acoustic reflection layer, a piezoelectric layer, an IDT electrode including a pair of comb electrodes, and wiring electrodes. The acoustic reflection layer includes a low Z dielectric layer, a high Z dielectric layer below the low Z dielectric layer and having an acoustic impedance higher than that of the low Z dielectric layer, and a metal layer above the low Z dielectric layer and having an acoustic impedance higher than that of the low Z dielectric layer. When the acoustic reflection layer is viewed in plan, in a region encompassing the IDT electrode and the wiring electrodes but no IDT electrodes other than the IDT electrode, an area including the metal layer is smaller than an area including the high Z dielectric layer. ## Claims ### Claim 1 An acoustic wave device comprising: a supporting substrate; an acoustic reflection layer directly or indirectly on the supporting substrate; a piezoelectric layer directly or indirectly on the acoustic reflection layer; one or more IDT electrodes directly or indirectly on the piezoelectric layer; and a wiring electrode directly or indirectly on the piezoelectric layer and electrically connected to the one or more IDT electrodes; wherein the acoustic reflection layer includes: a first dielectric layer; a second dielectric layer closer to the supporting substrate than the first dielectric is to the supporting substrate and having an acoustic impedance higher than that of the first dielectric layer; and a metal layer closer to the piezoelectric layer than the first dielectric layer is to the piezoelectric layer and having an acoustic impedance higher than that of the first dielectric layer; and when the acoustic reflection layer is viewed in plan, in a region that encompasses one of the one or more IDT electrodes and a wiring electrode connected to the one IDT electrode but does not encompass any IDT electrodes other than the one of the one or more IDT electrodes, an area in which the metal layer is provided is smaller than an area in which the second dielectric layer is provided. ### Claim 2 (depends on 1) The acoustic wave device according to claim 1, wherein each of the one or more IDT electrodes includes a pair of comb-shaped electrodes; and a film thickness of the piezoelectric layer is less than or equal to an IDT wavelength, which is defined by a pitch of a plurality of electrode fingers of one of the pair of comb-shaped electrodes. ### Claim 3 (depends on 1) The acoustic wave device according to claim 1, wherein the acoustic reflection layer further includes a third dielectric layer between the metal layer and the piezoelectric layer and has an acoustic impedance lower than that of the metal layer. ### Claim 4 (depends on 3) The acoustic wave device according to claim 3, wherein a film thickness of the third dielectric layer and a film thickness of the first dielectric layer are different. ### Claim 5 (depends on 1) The acoustic wave device according to claim 1, wherein the acoustic reflection layer includes: at least one of a plurality of the metal layers provided in a perpendicular or substantially perpendicular direction of the piezoelectric layer and a plurality of the second dielectric layers laminated in the perpendicular or substantially perpendicular direction; a fourth dielectric layer having an acoustic impedance lower than that of the plurality of metal layers and being respectively provided between the plurality of metal layers; and a fifth dielectric layer having an acoustic impedance lower than that of the plurality of second dielectric layers and being respectively provided between the plurality of second dielectric layers. ### Claim 6 (depends on 5) The acoustic wave device according to claim 5, wherein a film thickness of the fourth dielectric layer and a film thickness of the fifth dielectric layer are different. ### Claim 7 (depends on 1) The acoustic wave device according to claim 1, wherein the metal layer is made of Pt or W. ### Claim 8 (depends on 1) The acoustic wave device according to claim 1, wherein the first dielectric layer is made of silicon oxide. ### Claim 9 (depends on 1) The acoustic wave device according to claim 1, wherein the second dielectric layer is made of Ta2O5. ### Claim 10 (depends on 1) The acoustic wave device according to claim 1, wherein, when the acoustic reflection layer is viewed in plan, the metal layer is in a region that encompasses the one of the one or more IDT electrodes but does not encompass the wiring electrode. ### Claim 11 (depends on 1) A high frequency front end circuit comprising: the acoustic wave device according to claim 1; and an amplifying circuit connected to the acoustic wave device. ### Claim 12 (depends on 11) The high frequency front end circuit according to claim 11, wherein each of the one or more IDT electrodes includes a pair of comb-shaped electrodes; and a film thickness of the piezoelectric layer is less than or equal to an IDT wavelength, which is defined by a pitch of a plurality of electrode fingers of one of the pair of comb-shaped electrodes. ### Claim 13 (depends on 11) The high frequency front end circuit according to claim 11, wherein the acoustic reflection layer further includes a third dielectric layer between the metal layer and the piezoelectric layer and has an acoustic impedance lower than that of the metal layer. ### Claim 14 (depends on 13) The high frequency front end circuit according to claim 13, wherein a film thickness of the third dielectric layer and a film thickness of the first dielectric layer are different. ### Claim 15 (depends on 11) The high frequency front end circuit according to claim 11, wherein the acoustic reflection layer includes: at least one of a plurality of the metal layers provided in a perpendicular or substantially perpendicular direction of the piezoelectric layer and a plurality of the second dielectric layers laminated in the perpendicular or substantially perpendicular direction; a fourth dielectric layer having an acoustic impedance lower than that of the plurality of metal layers and being respectively provided between the plurality of metal layers; and a fifth dielectric layer having an acoustic impedance lower than that of the plurality of second dielectric layers and being respectively provided between the plurality of second dielectric layers. ### Claim 16 (depends on 15) The high frequency front end circuit according to claim 15, wherein a film thickness of the fourth dielectric layer and a film thickness of the fifth dielectric layer are different. ### Claim 17 (depends on 11) The high frequency front end circuit according to claim 11, wherein the metal layer is made of Pt or W. ### Claim 18 (depends on 11) The high frequency front end circuit according to claim 11, wherein the first dielectric layer is made of silicon oxide. ### Claim 19 (depends on 11) The high frequency front end circuit according to claim 11, wherein the second dielectric layer is made of Ta2O5. ### Claim 20 (depends on 11) A communication apparatus comprising: the high frequency front end circuit according to claim 11; and a signal processing circuit that processes a high frequency signal.